Various types of Doppler intrusion detection devices are known. For example, there is described in an article entitled: "A 10.5 GHz MIC DIRECTION SENSITIVE DOPPLER MODULE USING A GaAS FET AND A Ag/Pd THICK FILM" by T. MORI et al in IEEE Publication Code 0149-645X/81/0000-0319$00.75 1981, pp 319-321, a Doppler module employing a dielectric resonator and a waveguide cavity.
Other relevant publications include:
A Highly Stabilized Low-Noise GaAs FET Integrated Oscillator with a Dielectric Resonator in the C Band by H. Abe et al, IEEE Transactions on Microwave Theory and Techniques Vol. MTT-26, No. 3, March 1978;
A Highly Stabilized GaAs FET Oscillator Using a Dielectric Resonator Feedback Circuit in 9-14 GHz by O. Ishihara et al, IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-28, No. 8, August, 1980;
Review of Dielectric Resonator Oscillator Technology, by A. P. S. Khanna, 41st Annual Frequency Control Symposium--1987, Publication Code: CH2427-3/87/0000-478$1.00 1987, pp 478-486;
Ultrastable Low-Noise GaAs FET Oscillator with Dielectric Resonator by G. Lan et al RCA Review, Vol. 47, December, 1986, pp 473-486.
Microwave Doppler radar modules employing fixed frequency Gunn oscillators and mixer cavities are employed generally in Doppler radar systems.
More recently, dielectric resonators have been employed in oscillators in various microwave applications. Due to the relatively large parasitic field produced by dielectric resonator oscillators, they are normally enclosed within a metal box for shielding purposes. Reference is made in this context to U.S. Pat. No. 4,731,611 which describes stripline Doppler radar wherein the oscillator is sealed to prevent RF leakage.
The disclosures of the foregoing references are all incorporated herein by reference.